New "smart" polymer opens door for medical use of low-power near-infrared light

Researchers at the University of California, San Diego (UCSD) have conducted initial testing of a new "smart" plastic material which may bring about new uses in medicine for near-infrared (NIR) light. According to early experiments, the plastic material will break down into non-toxic particles in response to lower-power NIR light. This may lead to improved treatment of, for example, tumors, or improvements in the release of tracing compounds and imaging agents for improved medical diagnostics applications.

Anyone who has attempted to pick up a old plastic bag only to have it crumble into tiny fragments is aware that certain plastics degrade (break down) when subjected to things such as prolonged exposure to sunlight and oxygen. This property may have implications in medicine. Some forms of electromagnetic radiation (other than visible light) are able to pass through tissue.

The visible light which enables you to read this article is unable to do this as the photons are stopped by the skin, but other wavelengths of light pass through easily. High wavelength photons such as X and gamma rays can easily pass through very dense materials, including the body, though they affect tissue in the process by ionizing it. Other forms of electromagnetic radiation can produce varied effects: for example, significant amounts of infrared radiation can cause damage in the form of heat.

Just beyond the wavelength of visible light, however, is NIR. NIR light is a non-ionizing form of electromagnetic radiation able to pass through skin and up to four inches of tissue. This property of NIR light enables it to be of use in near-infrared spectroscopy and imaging, both of considerable use in medicine. In response to lower-power NIR, the plastic material being explored by the UCSD researchers will break down into non-toxic particles. Significantly, this will occur at levels of lower-power NIR light exposure which are "biologically benign".

New medical uses

This may enable the construction of "microdevices" such as hydrogels able to release medicinal compounds to surrounding tissues, at precise locations and timings, which could lead to improved treatment of, for example, tumors, or improvements in the release of tracing compounds and imaging agents for improved diagnostics.

The research team from the Laboratory for Bioresponsive Materials, led by Adah Almutairi claim, "to the best of our knowledge, this is the first example of a polymeric material capable of disassembly into small molecules in response to harmless levels of irradiation."

The UCSD team's research was published in September 2011 in the ACS journal Macromolecules.

The "smart" material breaks down into non-toxic particles in response to NIR light (Image: American Chemical Society)

The "smart" material breaks down into non-toxic particles in response to NIR light (Image: American Chemical Society)

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